General Category > Quadrajet Carb Talk and Tips
1973 800 CFM Mods
Jim Rodgers:
Engine.
My goal is a stock appearing 9. I feel like I am leaving something on the table with this carb and I am hoping you guys can point me in the right direction.
willie:
beautiful work,if cliff can offer any advice he probably will.He seems to be a great very smart guy.I do not have the experence to be of any help.I am still learning myself,good luck. willie
Cliff Ruggles:
Something isn't quite right someplace. I say this because of the jetting required to get a clean fuel curve, and MPH is down some.
I've used the large Buick castings with the booster rings removed, but never touched the castings otherwise or went to larger throttle plates.
At least one of the cars that uses them runs high 9's at over 135mph. It has 71 main jets and custom machined secondary metering rods in it.
The owner has a full set of custom machined rods from .028" to .055" in .003" incriments for fine tuning at the track.
I'm thinking the mechanical pump may be too restrictive and the carb isn't staying full on hard runs.
Could need smaller airbleeds as well, to get more fuel and less air.
Could also be the specific mods to the carb choke housing and primary bores, but not sure?.....Cliff
Jim Rodgers:
The factory pump has been gutted. The 1/2" aluminum line just goes into the pump bowl and loops back out. Sitting still my fuel system will pump a gallon to the carb inlet in 15 seconds. But I realize the carb could still be going dry.
I wish I could find one of those 135 mph qjets to borrow to test back to back with mine. Or send mine off to be tested.
Cliff, is there a way to bench test these carbs?
Cliff Ruggles:
Not really. The dynamic test always prevails anyhow (track runs). No matter what the carb does on the dyno, it will act differently at the track.
A carb sitting on a car capable of low 10 second runs, is like holding a glass of water in your hand and getting shot out of a cannon. Imagine what the fuel inside the carb is trying to do? Let alone the fuel in the tank, lines, etc......Cliff
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